A known die-casting technique to form an impeller by a lost wax casting process is disclosed in US2006/0291996A (hereinafter referred to as Reference 1). The impeller is generally adapted to a pump rotationally driven by a predetermined drive source so as to send fluid such as water and the like, or is generally adapted to an axial flow rotor such as a gas turbine engine and the like rotationally driven by operating fluid. In particular, the impeller disclosed in Reference 1 is an impeller of a supercharger for an engine and is made of metal or the like. A die for injection-forming a sacrificial pattern utilized to die-cast the impeller is explained in Reference 1.
The die includes slide dies each slidably supported by a slide support and rotatable about a rotational axis extending along a radial direction of the impeller. The slide die includes plural cores for forming blade surfaces of blades of the impeller. The cores are rotated about the rotational axis relative to the slide support in such a way that the blade surfaces may be formed to have cross sections which extend along a flat surface perpendicular to the radial direction of the impeller so as to be inclined to a rotational axle of the impeller.
After the injection-forming process, the slide supports are moved to an outward side in the radial direction of the impeller; therefore, the cores are separated from the die-cast blade surfaces to the outward side in the radial direction while rotating about the rotational axes extending along the radial direction.
In addition, a cam plate including plural cam grooves being radially curved is rotatably arranged around the rotational axle of the impeller. The cam grooves are engaged with respective lower surfaces of the slide supports. The cam plate serves as a mechanism to separate the plural cores in conjunction with one another from the die-cast impeller toward the outward side in the radial direction.
For example, the die-casting technique disclosed in Reference 1 needs a complex and elaborate mechanism including bearings and the like so that the cores may rotate without resistance when the cores are removed from the die-cast impeller. Additionally, a mechanism to position each of the cores at a predetermined angle before the injection-forming process is required to the die-casting technique disclosed in Reference 1; therefore, the manufacturing cost of a die-casting device may increase.
Moreover, according to the die-casting technique disclosed in Reference 1, the aforementioned cam plate needs to be rotated about the rotational axle in order to remove the plural cores in conjunction with one another from the die-cast impeller. Accordingly, the cam plate may not serve as a drive source for moving a movable die covering upper ends of the blades to an upper side of the impeller after the impeller is formed by die casting. In addition, according to the die-casting technique disclosed in Reference 1, the cores are moved toward the outward side in the radial direction; therefore, a large space may be required in the radial direction of the impeller.
A need thus exists for a molding device and a molding method for forming an impeller, which are not susceptible to the drawbacks mentioned above.